Increased Vitamin D Binding Protein Expression in JIA Patients Suffering Disease Extension

Background: Juvenile idiopathic arthritis (JIA) comprises a poorlyunderstood group of chronic, childhood onset, autoimmune diseaseswith variable clinical presentations, outcomes and therapeuticresponses. Current laboratory tests are unable to flag those patientsat a higher risk of disease spread to multiple joints, who could benefitform earlier therapy to prevent joint damage. This study was focusedon profiling the synovial fluid (SF) proteome associated with diseaseextension from oligo- to polyarticular status by a difference gelelectrophoresis (DIGE) approach.Methods: To construct a discriminant model, SF samples from 55 JIApatients were analysed: 30 oligo-, 8 extended oligo- and 17polyarticular disease. Initial SF samples from each patient werelabeled with Cy dyes and subjected to protein separation by 2-DE. Theability to distinguish patients at risk of disease extension by a selectgroup of proteins was illustrated by multivariate analysis methods.Proteins over expressed with a two-fold difference between patientsubgroups were identified by MALDI-TOF. Specific antibodies wereused to validate putative biomarker expression in synovial fluid bywestern immunoblotting and in synovial membrane (SM) byimmunohistochemistry.Results: Samespots software analysis of SF gel scans was used tohighlight joint-specific proteins which were differentially expressedacross disease classifications. Hierarchical clustering based on theexpression levels of a previously selected set of 40 proteins matchedacross the three clinical subgroups segregates the extended oligoarticularpatients. Proteolytic fragments of apolipoprotein AII, complementcomponent C3c and vitamin D binding protein were identified(P